Nematodes: ATTRA Alternative Controls A Publication of ATTRA - National Sustainable Agriculture Information Service • 1-800-346-9140 • www.attra.ncat.org By Martin Guerena This publication provides general information on the tiny worm-like organisms called nematodes. It NCAT Agriculture contains detailed descriptions of the genera of nematodes that attack plants, as well as various methods Specialist to diagnose, discourage, and manage plant parasitic nematodes in a least toxic, sustainable manner. © 2006 NCAT Contents Introduction Introduction ..................... 1 ematodes are Symptoms and tiny, worm-like, Sampling .......................... 4 Nmulticellular Preventing Further animals adapted to liv- Spread of Nematodes ....................... 4 ing in water. The num- ber of nematode species Managing Soil Biology ............................... 5 is estimated at half a Crop Rotations and mil lion, many of which Cover Crops ...................... 6 are “free-living” types Botanical found in the oceans, Nematicides ..................... 9 in freshwater habitats, Biocontrols ...................... 10 and in soils. Plant-par- Plant Resistance ............11 asitic species form a Red Plastic Mulch ......... 12 smaller group. Nema- www.insectimages.org Solarization .................... 13 todes are common Flooding .......................... 13 in soils all over the Root-knot nematode—Meloidogyne brevicauda Loos Summary ......................... 13 world (Dropkin, 1980; ©Jonathan D. Eisenback, Virginia Polytechnic Institute and State University References ..................... 14 Yepsen, 1984). As a commentator in the early Further Resources ........17 twentieth cen tury wrote: genera and species have particu lar soil and Web Resources ..............17 climatic requirements. For example, cer- Suppliers .......................... 18 If all the matter in the universe except the tain species do best in sandy soils, while nematodes were swept away, our world would oth ers favor clay soils. Nematode popula- still be dimly recognizable, and if, as disembod- tions are generally denser and more preva- ied spirits, we could investigate it, we should fi nd lent in the world’s warmer regions, where its mountains, hills, valleys, rivers, lakes and ATTRA—National Sustainable longer growing seasons extend feeding peri- Agriculture Information Service oceans represented by a thin fi lm of nematodes. ods and increase reproductive rates (Drop- is managed by the National Cen- (Sasser, 1990) ter for Appropriate Technology kin, 1980). In the southern United States, (NCAT) and is funded under a grant from the United States as many as ten generations are produced in Department of Agriculture’s An important part of the soil fauna, nem- one season (Yepsen, 1984). Rural Business-Cooperative Ser- vice. Visit the NCAT Web site atodes live in the maze of interconnected (www.ncat.org/agri. channels—called pores—that are formed Light, sandy soils generally harbor larger html) for more informa- popu lations of plant-parasitic nematodes tion on our sustainable by soil processes. They move in the fi lms agriculture projects. /$"5 of water that cling to soil particles. Many than clay soils. This is attributable to more effi cient aeration of sandy soil, fewer wide variety of plant-pathogenic fungi and or ganisms that compete with and prey on bac teria. These microbial infections are nema todes, and the ease with which nem- often more economically damaging than the atodes can move through the root zone. direct effects of nematode feeding. Also, plants grow ing in readily drained soils are more likely to suffer from intermit- tent drought, and are thus more vulnerable Major Plant-Parasitic Nematode to parasitic nematodes. Desert valleys and Genera in the U.S. and Associated tropical sandy soils are particularly chal- Damage to Plants lenged by nematode overpopu lation (Drop- kin, 1980). • Root-knot nematodes (Meloidogyne species) form galls Plant-parasitic nematodes—the majority of on injured plant tissue. The galls which complete their lifecycles in the root block water and nutrient fl ow zone and feed upon the roots—are found to the plant, stunting growth, in association with most plants. Some are impairing fruit production, and endoparasitic—living and feeding within causing foliage to yellow and wilt. the tissue of roots, tubers, buds, seeds, etc. Roots become rough and pimpled Related ATTRA (Sasser, 1990) Others are ectoparasitic, and susceptible to cracking. Publications feeding externally through plant walls. A single en doparasitic nematode can kill a • Cyst nematodes (Heterodera Biointensive species) give plants an unthrifty Integrated Pest plant or reduce its productivity, while sev- or malnourished appearance, and Management eral hundred ectopara sitic nematodes might feed on a plant without seriously affecting cause them to produce smaller- Sustainable Soil than-normal tops. Foliage is lia- Management production (Ingham, 1996). A few spe- cies are highly host-specifi c, such as Het- ble to wilt and curl, while roots Sustainable erodera glycines on soybeans and Globodera become thick and tough and take Management of Soil- rostochiensis on potatoes (Sasser, 1990). on a red or brown coloring. Borne Plant Diseases But in general, nematodes have a wide • Sting nematodes (Belonolaimus Alternative Soil host range. species) are found mainly in the Amendments Endoparasitic root feeders include such South, especially in sandy soils Manures for Organic economi cally important pests as the root- with meager organic-matter Crop Production knot nematodes (Meloidogyne species), content. Areas of stunted plants are an early indicator. As these Overview of Cover the cyst nematodes (Heterodera species), Crops and Green and the root-lesion nema todes (Prat- areas grow larger and fi nally Manures ylenchus species). (Sasser, 1990) Important meet, the plants that were fi rst ectoparasitic root feeders include: root aff ected will start to die at the (Paratrichodorus and Trichodorus), dag- margins of older leaves. ger (Xiphinema), needle (Longidorus, • Root-lesion (Pratylenchus Paralongidorus), ring (Criconemella, Mac- species) cause internal brown- roposthhonia), stunt (Tylenchorhynchus and ing in potato tubers and in the Merlinius), pin (Paratylenchus), and spiral roots of corn, lettuce,peas, carrots, (Helicotylenchus, Rotylenchus, and Scutello- tomatoes, and brassicas. nema) nematodes. Direct feeding nematodes (Yepsen, 1984) can drastically decrease a plant’s uptake of nutrients and water. Nematodes have the greatest impact on crop productivity when they attack the roots of Nematode control is essentially prevention, seedlings immediately after seed germina- be cause once a plant is parasitized it is tion (Ploeg, 2001). Nematode feeding also impossible to kill the nematode without also creates open wounds that provide entry to a destroying the host. The most sustainable Page 2 ATTRA Nematode: Alternative Controls ©Ulrich Zunke, www.mactode.com ©William Wergin, www.mactode.com Spiral nematode, Helicotylenchus sp. Pratylenchus sp. larva and egg. ematodes have the Ngreatest impact on crop pro- ductivity when they attack the roots of seedlings immedi- ately after seed germination. ©Jonathan Eisenback, www.mactode.com ©Michael McClure, www.mactode.com Face view of lance nematode, Hoplolaimus sp. Sugarbeet cyst nematode juvenile. ©Ulrich Zunke, www.mactode.com ©Jonathan Eisenback, www.mactode.com Lesion nematodes penetrating a root. Mononchoid nematode feeding on another nematode. www.attra.ncat.org ATTRA Page 3 approach to nematode control integrates type of nematode causing damage, and several tools and strategies, including cover the time of the season. The procedure pre- crops, crop rotation, soil solarization, least- sented here is a generic sampling technique toxic pesticides, and plant varieties resistant for annual crops. Soil samples taken in to nematode damage. These methods work the late sum mer are best when testing for best in the context of a healthy soil envi- the presence of nema todes. Root-zone soil ronment with suffi cient organic matter to samples are best taken im mediately after support diverse populations of microorgan- harvest, or just prior to harvest if the crop isms. A balanced soil ecosystem supports a shows signs of damage. First, fi elds should wide variety of biological control organisms be divided into 20-acre blocks with similar that helps keep nematode pest populations damage, soil texture, or cropping history. in check. From each block take several sub-samples, mixing them well to create a single one- Symptoms and Sampling quart sample for each block. Soil samples should be kept cool, but not frozen. Usually, sampling is done because the grower observes a section of field with Samples for established perennial crops are t is important to unhealthy plants, or notices an unexplained best taken from the feeder root zone, which note that spe- yield reduction. Be cause nematodes dam- is usually located around the canopy drip age roots, any condition that stresses the line (Dropkin, 1980). Your county or state cies of nema- I plant—such as drought (or even hot spells), Cooperative Extension Ser vice can provide tode are present in fl ooding, nutrient defi ciencies, or soil com- names of commercial labs that have nema- all soils. paction—will tend to amplify the damage tode-identifi cation services. symptoms noted above. Failure to respond normally to fertilizers and slower-than-nor- Preventing Further Spread mal re covery from wilting are signs of nem- atode